As a power source used in a mechanical field in which a large power is required while at work such as a machine tool field or a cargo handling machine field, conventionally there exists such a tendency that the power source has changed from hydraulic type to electric type with the advance of the times, from the standpoints of both high response speed and clean energy. However, in the case where the power source is used by placing great importance on large power generation and long power duration rather than response speed, hydraulic source is still used, in spite of the fact that there exists a problem with respect to piping arrangement and power intermission. This is because although the electric power source is superior to the hydraulic power source from the standpoint of easiness in wiring and power control, since a large-sized direct-driven type actuator and a large capacity storage function are both required to generate large power and to control the generated large power autonomically, the electric power source is inferior to a pressurized power source from the standpoints of size and stability at the present stage. Further, although it may be possible to consider to combine both merits of the hydraulic power source and the electric power source appropriately, such a power source as described above has been not yet reported.
In the field of machine tools, for instance, as a method of fixing an object to be machined (referred to as "workpiece", hereinafter) to a jig mounted on a table of the machine tool, it is general to fasten a workpiece manually by use of a screw or a cam (referred to as "clamping", hereinafter). However, a method of clamping a workpiece by use of a hydraulic cylinder has been adopted partially to automatize the fixing of the workpiece to the jig.
FIG. 43 is a diagrammatical structural view showing a first prior art machine tool, on which a hydraulic type workpiece clamping device for clamping the workpiece by use of a hydraulic cylinder is mounted.
In FIG. 43, a machine tool 100 includes a hydraulic source 104 composed of a first hydraulic cylinder 103a for clamping the right end of a workpiece 120, a second hydraulic cylinder 103b for clamping the left end of the same workpiece 120 both mounted on a pallet 101, a hydraulic pump 104a, a hydraulic tank 104b, a solenoid valve 104c, a hydraulic motor 104d for driving a hydraulic pump 104a, and a hydraulic switch (not shown), etc.; a first hydraulic pipe 106a for communication between the first hydraulic cylinder 103a and the hydraulic source 104; and a second hydraulic pipe 106b for communication between the second hydraulic cylinder 103b and the hydraulic source 104. In the machine tool 100, a hydraulic pressure can be generated by driving the hydraulic driving motor 104a, and the generated hydraulic force is transmitted through the first and second hydraulic pipes 106a and 106b, respectively to move two rods of the first and second hydraulic cylinders 103a and 103b in the downward direction in FIG. 43, respectively, that is, to clamp a workpiece 120.
In the above-mentioned machine tool 100, however, since hydraulic pressure is transmitted from the hydraulic source 104 to the first and second hydraulic cylinders 106a and 106b, respectively, the first and second hydraulic pipes 106a and 106b are indispensable, thus causing the following problems: (1) in the case of a pallet jig of a horizontal machining center and a jig of a transfer machine, since the jig is moved freely without relation to the movement of the machine tool, it is particularly difficult to arrange the hydraulic piping from the hydraulic source to the respective hydraulic cylinders. Accordingly, in the case of these machine tools, it is hardly possible to clamp workpiece by use of the hydraulic cylinders. (2) as a special example, there exists a method of using a hydraulic check valve for disconnecting hydraulic pressure between the hydraulic check valve and the hydraulic source by use of a hydraulic coupler. In this method, however, since a relatively large device is required to operate the hydraulic coupler automatically, this method is not practical and therefore not used widely.
On the other hand, such a method may be considered that a workpiece is clamped automatically by use of only electric energy (without use of the hydraulic pressure). In this method, however, as already explained, since the direct-driven type large-capacity actuator and a power storage unit (as an accumulator for maintaining the generated force) have been both not yet developed, this method is not yet put into practical use.
Accordingly, it is the object of the first and third inventions to provide a hydraulic source and a machine tool provided with the same hydraulic source which can be used even when a jig is movable freely.
Further, recently, in a workshop where machine tools are arranged and handled, the setup process of the machine tools has been automatized more and more securely, because of various social background such as the unclean working environment, lack of laborers, change in production mode to multi-model small-quantity production, etc. However, the hydraulic source has been mainly used as the power source for an actuator required to generate a large force, as in the case of a free-end tool of an automatic jig or an industrial robot. Further, in general, the hydraulic actuator is driven by a hydraulic pump pressurized by a motor. Therefore, the hydraulic piping and the electric wiring are both inevitably required. This causes a problem with respect to the connection and disconnection of the hydraulic piping and the electric wiring, when the automatic jig is moved autonomically or when the hydraulic actuator driving, means is moved autonomically or when the free-end tool of an industrial robot is exchanged. To overcome this problem, recently an automatic coupler has been put into practice.
Even when the hydraulic couplers are used, however, since there still exists a necessity of the hydraulic piping arrangement and the electric wiring between the hydraulic actuators and the driving means. In addition, the problem related to cutting lubricant leakage is not yet solved perfectly, and the automatization of the hydraulic coupler operation is rather difficult. Accordingly, when an autonomous movement of the hydraulic actuator relative to the driving means or when the exchange of the free-end tool of the industrial robot is considered, there still remains a problem with respect to the reliability. Further, there exists another problem in that since the number of couplers increases with increasing number of jig actuators, when data signals are not transmitted in parallel to each other, the reliability of the apparatus decreases and the size of the apparatus increases.
Accordingly, the object of the fourth to tenth inventions is to provide an universal hydraulic apparatus which can move the hydraulic actuator autonomically and enables the tool exchange, without causing any problems in the hydraulic piping arrangement and the electric wiring arrangement between the hydraulic actuator and the driving means, in spite of a simple construction; in other words, to provide a unit-type hydraulic source of the first to third inventions.
Further, in the fields of the machine tools and the cargo handling machines, the power source has been changed from the hydraulic method to the electric method with the advance of the times from the standpoints of the high response speed of the actuator and the clean energy. However, in general, as the power for driving the devices for directly handling workpiece such as a gripper, clamper, chuck, etc., pneumatic pressure is still used widely due to the simple mechanism, the easiness of torque and pressure control, etc. in spite of the fact that there exists a problem with respect to the piping arrangement and the power intermission. This is because although the electric actuator is superior to the pneumatic actuator-in the wiring and power connection and disconnection, since the electric actuator is of rotary type basically, a mechanism mounted on the end of the clamping and fastening devices is complicated and large-sized. For instance, when a workpiece is fixed to a jig mounted on a table of a machine tool, although, in general, the workpiece is clamped manually by use of a screw or a cam, a pneumatic clamping or a vacuum chucking is partially adopted for automatization of fixing the workpiece onto the jig. In this case, a compressor is generally mounted on the fixed side to compress air, and the compressed air is fed to a pneumatic actuator (i.e., cylinder) via a pressure regulator and an electromagnetic valve. Or else, a vacuum is generated by a vacuum generator to chuck the workpiece to the pallet by a pressure difference between the generated vacuum and the atmospheric pressure.
Accordingly, in any cases, the piping arrangement from the compressor to the damper or the suction unit is necessarily required. However, in the case of the pallet jig of the horizontal machining center or the jig of the transfer machine, since the pallet (jig) is moved, the above-mentioned piping is disabled. As a result, the pneumatic power has been not so far used to fix the workpiece. Further, when the griper clamps a workpiece and further moves as with the case of the direct-driven loader, the gripper pneumatic actuator or the vacuum pad must be connected to the fixed side pneumatic source through a piping disposed in a cable bear (support) movable together and in parallel to the movable portion. Such construction causes an increase of the initial investment for the supplementary equipment (e.g., duct) and a decrease in the long-term reliability of many-hour operation of the apparatus.
Further, when the clamping jig of the machining center is moved by use of pneumatic pressure, since the pressure is not required at places other than specific positions, after a workpiece has been once fixed, it is not necessarily to drive the compressor, as far as the pressure can be maintained. Therefore, when the power supplying unit for supplying power to the compressor driving motor is mounted on a specific position and further the electric power can be supplied automatically, it is possible to control the workpiece fixing unit (pallet) autonomically by a simple construction.
Accordingly, the object of the eleventh to fourteenth inventions of the present invention is to provide an autonomous pneumatic source obtained by developing the third invention hydraulic source horizontally to the pneumatic source, on the basis of a novel idea related to the pneumatic driving system such that electric power and data can be transmitted through a simple coupling, without use of any electrodes, which can be replaced with the conventional method such that the complicated piping is arranged and the pneumatic couplers and valves are operated manually.
Further, in the case of a rotary table, in particular of an index table (rotation indexing) used in the machine tool or the assembly process, the electric power and the data are transmitted through wires arranged between the fixed portion and the rotary portion, by limiting the moving range of the wires. Therefore, although the rotary table can be rotated in both forward and reverse directions to some extent, it is impossible to rotate the rotary table without any rotational limitation or at a high rotational speed, thus causing a problem in that the wires are disconnected due to fatigue. To overcome these problems, that is, to enable a multi-rotation rotary table to some extent, although a contact transmission method by use of springs has been so far adopted, in practice there still exists a problem in that the characteristics of the contact portions tend to deteriorate due to an unclean environment such that there exist moisture and chips, so that it has been impossible to increase the rotational speed of the table more than 10 to 50 r.p.m. In addition, when signals are transmitted, since contact noises are inevitably generated, the characteristics thereof have been improved by inserting filters or by severely selecting the contact material. Further, in the case where a rotary coupling as shown in FIG. 44 (described later) is used, in particular when a plurality of actuators (jig, motor, nozzle, etc.) are controlled independently and separately, since it is necessary to assemble a number of hydraulic circuits in correspondence to the number of actuators within a limited space in the rotary coupling, there exists a practical problem in that the hydraulic sealing is difficult in addition to an increase in size and therefore an increase in cost thereof.
Accordingly, the object of the fifteenth to sixteenth inventions of the present invention is to provide a rotary table on which the hydraulic source of the first to third inventions are mounted, which can solve the problems related to the above-mentioned power and data transmission, secure long-term reliability and stability, and improve the table rotational speed on the basis of signal transmission, without use of any electrical contacts, and further which can remove the complexity of the multi-circuit construction of the rotary coupling, by replacing the non-electromagnetic power control with the electric power (electromagnetic valve) control.
Further, FIG. 45 is a perspective view showing a second example of the prior art direct-driven type loader. As shown in FIG. 45, a movable unit 112 of the direct-driven type loader body is movably supported by two travel rails 111 arranged in an x-axis direction, and driven reciprocatingly in the x-axis direction by driving an x-axis servomotor (not shown) mounted inside the movable unit 112. At the lower end portion of the movable unit 112, a gripper 118 for gripping a workpiece driven by fluid pressure such as hydraulic or pneumatic pressure is disposed so as to be movable in a z-axis direction by a z-axis servomotor 113 and rotatable in a .theta. direction by a .theta.-rotation servomotor 116, respectively. Further, a power source for supplying power to the above-mentioned respective servomotors 113 and 116, a hydraulic pressure source for supplying a fluid pressure to the gripper 118, and a control unit for controlling the respective servomotors 113 and 116 and the gripper 118 are all disposed outside the movable unit 112. On the other hand, a cable duct 151 is disposed in parallel to the travel rails 111. Further, respective electric wires 155 electrically connected to the power source and the control unit to drive the respective servomotors 113 and 116, and fluid pipes 156 connected to a fluid pressure source to drive the gripper 118 are all mounted on a cable duct 151 under the condition that these are accommodated in a cable bear (support) together, in order to supply power and transmit data to the respective servomotors 113 and 116 and to supply fluid pressure to the gripper 118, respectively. However, in the second prior art example as described above, since the movable unit 112 is driven via the various electric wires connected to the power source and the control unit disposed outside the movable unit and via the fluid piping connected to the fluid pressure source disposed outside of the movable unit, the following problems arise: since the movable unit is moved together with the various electric wires and fluid pipes, when the movable distance is long, the weight of the cable bear is heavy, so that the a sufficient strength and a large driving power are required to support and move the cables and wires. In addition, since bending stress is applied to the various electric wires and the fluid pipes whenever the wires and cables moved reciprocatingly, the various electric wires and fluid pipes tend to be damaged or broken. In particular, when the loader is driven at a high speed (required recently, in particular), the electric wires and the fluid pipes are often damaged, thus causing a problem in that loss increases due to maintenance and operation stop whenever the wires and pipes are broken. To overcome these problems, although an electrode contact power feeding method (e.g., contactor, trolley, etc.) has been tried, not only the stable power feeding and stable data transmission cannot be realized, but also there arises a problem in that contact portions of the electrodes are worn away so that the stability deteriorates, under such an unclean environment that cutting lubricant and chips inevitably exist. Further, when the movable unit is moved by use of a rack and pinion mechanism, in particular, it is possible to mount a plurality of the movable units on the same travel rails and to drive the movable units simultaneously within a non-interference range (cooperation control) in principle. In practice, however, it has been difficult to realize this cooperation control due to the problem related to wires and pipes connected to the movable unit and the cable bear arrangement.
Accordingly, the object of the seventeenth to eighteenth embodiment of the present invention is to provide a direct-driven type loader which can improve the reliability and enables a cooperation control of a plurality of movable units, without laying the electric wires and the fluid pipes between the movable unit and external power source and control unit and without need of a large-scale installation; that is, a direct-driven type loader to which the first to third inventions are applied.
Further, in the prior art machine tool, there exists a problem with respect to means for aligning a workpiece. In more detail, in the machine tools such as a vertical lathe, gear hobbing machine, turning center, etc., a workpiece to be cut is first fixed on a table of the machine tool and then a cutter is pushed against the workpiece by turning the table to cut the fixed workpiece. In this case, prior to cutting, the cutting center of the cut workpiece must be aligned at a central position of the table at a high precision and then fixed to the table.
Conventionally, in this workpiece locating and fixing process, first the workpiece is fixed to the table temporarily; the table of the machine tool is turned; the cutting center position is measured by use of a measurement gage mounted on the spindle of the machine tool to calculate the misalignment rate relative to the center of the turntable; and then the misalignment rate is reduced by repeating the same operation manually by a worker. Therefore, a long time and an experiment has been so far required for the workpiece alignment.
However, there exists a need of eliminating, that is, automatizing this setup work due to the social background that the number of skilled worker has decreased and further been aged, and further a need of increasing the availability factor of the machine tool becomes strong.
In the case of the machining center in the machine tools, a pallet exchange apparatus composed of a pallet changer, a pallet pool, etc. has been widely used for automatization of the setup work (tool exchange work). In the case of the machine tools such as vertical lathe, the gear hobbing machine, turning center, etc., on the other hand, although the machining center position must be aligned with the center position of the turntable precisely, in the case of the locating and fixing method used for the pallet exchange (adopted for the general machining center), there exists a limit in precision of the alignment of both the central positions, even if the respective part machining precision of the machine tool and the pallet exchange apparatus are increased to the respective extreme situations.
Accordingly, the object of the nineteenth to twentieth inventions of the present invention are to provide a workpiece locating and clamping apparatus for locating a workpiece mounted and fixed onto the pallet, by clamping the workpiece periphery with the use of a plurality of actuators and by driving and controlling these actuators on the basis of fluid pressure such as hydraulic or pneumatic pressure caused by power feeding and data transmission through the hydraulic coupling from outside of the fixed portion or by non-contact high-frequency electromagnetic induction from outside of the turntable; that is, to provide a dependent invention related to the hydraulic source of the first to third inventions.